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102 Growth & Development > Lecture 5 > Flashcards

Lecture 5 Flashcards

How do plants perceive and respond to light stimuli? Plants have several receptor pigments that perceive light and control behavior and development. They do this partly by regulating gene expression.

1
Q

true or false; plants can “see” light

A

true

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2
Q

What does plants seeing light affect

A 
germination
seedling development
phototropism
photosynthesis 
shade avoidance
flowering 
circadian rythmns
photmorphogenesis
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3
Q

What does it mean by photomorphogenesis

A

creation of form in the light

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4
Q

define nutation

A

circular swaying movement of the tip of growing shoot

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5
Q

true or false; light induces morphological changes in seedlings

A

true

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6
Q

What do you call the creation of form, of seedlings grown in the dark

A

skotomorphogenesis or etiolation

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7
Q

describe the characteristics of the seedlings grown in the dark

A 
tall
leaves are yellow green
chloroplasts are not properly developed
little chlorphyll
leaves are not fully expanded or open
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8
Q

What do you call the creation of form in the light

A

photomorphogenesis

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9
Q

What happens eg. in potatoes when the growing conditions of plants are shifted from dark to light

A

plants undergo de-etiolation

  • sprouting potatoes in the dark
  • shoots greening up in the light
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10
Q

Why is harmful to eat green potatoes

A

solanine is present in the green areas

  • can occur in improperly stored potatoes
  • solanine is harmful when ingested and can be toxic in large quantities
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11
Q

true or false; environment has the a large effect on the expression of a plants’ genes

A

true

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12
Q

define germination

A

beginning of growth by seed

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13
Q

define photosynthesis

A

conversion of light energy to chemical energy

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14
Q

true or false; wavelengths and the light intensity that plants perceive have a great impact on their growth

A

true

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15
Q

What wavelength affects photosynthesis

A

400-700nm is photosynthetically active radiation

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16
Q

What does it mean by phototropism

A

growth towards the light

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17
Q

What wavelength and light color affects phototropism

A
  • blue light causes plant to bend towards the light
  • multiple photoreceptors are involved in detecting the blue light
  • experiment called: determining the action spectrum (allows us to determine the wavelength perceived by a plant)
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18
Q

what light causes plants to grow out of the shade and into the light

A

far red light

19
Q

what light do green leaves absorb

A

red light

  • increases the proportion of far red light relative to red light
  • this is detected by the plants and they grow to taller to out compete other plants
20
Q

What are the light receptors in humans

A

humans have 4 light receptor pigments

  • 3 for each of the primary colors in our cone cells in the retina
  • 1 in our rod cells
21
Q

true or false; plants also have many photoreceptors for blue and red light

A

true

22
Q

What are phototropins

A

detect blue light

23
Q

what are phytochromes

A

detect red light

24
Q

What are cryptochromes

A

detect blue light

25
Q

Describe the structure of phytochromes

A
  • is a dimer
  • 2 identical proteins that are dimerized together to become one big molecule
  • each protein has a domain ( 2 domains in total); for photoreceptor activity and kinase activity
  • each molecule is attached to a chromophore
  • activated by light
26
Q

What is a chromophore

A

detects light

organic molecule

27
Q

true or false; there are two forms of phytochrome that absorb different wavelengths

A

true

28
Q

What are the two forms of phytochrome

A

Pr (660 nm)

Pfr (730nm)

29
Q

What does Pr absorb

A

red light

30
Q

what does Pfr absorb

A

far red light (longer wavelength)

31
Q

true or false; phytochrome is a molecular switching mechanism

A

true

32
Q

true or false; Pfr is the biologically active form of phytochrome

A

true

33
Q

what reverses phytochrome

A

light

34
Q

What happens in the dark to Pfr

A

slowly reverses to Pr

- slowly degraded and made

35
Q

what are the applications of studying light regulation of plant development

A

designing

selecting crops that can cope with being crowded

36
Q

true or false; most leaves are specialized for light absorption

A

true

- like a solar panel, leaves are often broad and flat to optimize light harvesting

37
Q

how come modern maize plants can be planted at high density; increasing their yield per hectare

A

Plants selected by plant breeders have upright leaves to help capture sunlight energy under crowded conditions.
They can be machine planted at high density (up to 100 000 plants per hectare)

38
Q

What is the effect of red light

A

increased germination
inhibit stem elongation and lateral root formation
stimulates leaf expansion, cholorplast development, red flower coloration, spore germination

39
Q

What is the effect of far red light

A

inhibits germination

40
Q

what is the photoreceptor responsible for perceiving red and far red light

A

phytochrome

41
Q

What does the kinase domain trigger

A

triggers kinase cascade

of downstream events

42
Q

What are phototropism involved in

A

phototropism

43
Q

what is the survival advantage of etiolation

A

increases the plants’ chances of reaching light before their stored energy supplies are exhausted

102 Growth & Development (10 decks)

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